package setvlet;

import pojo.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

@WebServlet(urlPatterns ={"/user"} )
public class UserServlet extends HttpServlet {
    //alt+insert

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<User> users=new ArrayList<>();
        //jdbc数据库操作 查询
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");

            //2、获取连接
            Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=utf-8",
                    "root","lpy20050217");

            //3、编写sql语句
            String sql = "select * from user";

            //4、预处理sql  .var
            PreparedStatement preparedStatement = connection.prepareStatement(sql);

            //5、如果有参数，设置参数

            //6、执行sql语句
            ResultSet resultSet = preparedStatement.executeQuery();

            // 7、如果是查询就遍历结果/如果是增删改 判断是否成功
            while (resultSet.next()) {
                User user=new User();
                user.setId(resultSet.getInt(1));
                user.setName(resultSet.getString(2));
                user.setPass(resultSet.getString(3));
                users.add(user);
            }
            // 8、返回视图
            resultSet.close();
            preparedStatement.close();
            connection.close();

            //把集合中的数据存储到作用作用域中
            req.setAttribute("users",users);
            req.getRequestDispatcher("/user.jsp").forward(req,resp);

        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }


    }

    }

